1. Field
This disclosure relates to methods, systems, and computer program products that collect and display non-contiguous data stored across multiple storage mediums.
2. Description of Background
A mainframe storage architecture commonly includes one or more disk volumes that store data. A volume table of contents (VTOC) is a data structure that resides on one or more of the disk volumes. The VTOC includes records known as data set control blocks (DCSB) that describe the data sets (files) on each of the disk volumes as well as size, location, and permissions of the files. The VTOC can reside anywhere on the disk volume. The first record on the first track of the first cylinder of any disk volume is traditionally called a volume label and includes a pointer to the location of the VTOC. The VTOC is added to the disk volume when the disk volume is initialized.
To locate a file on any particular disk volume, a program will generally interrogate a main catalog to find a location of the disk volume where the file resides. Having found the correct value, the VTOC is interrogated to find where on the disk the data is stored.
A file can be stored on one or more disk extents. An extent is a segment of storage on the disk device. The file can be stored across multiple disk volumes. Printing the extents per file is useful for development, testing, and customer problem diagnostics. Currently there exists no method for retrieving all multi-volume extents per file. At best, the conventional methods print only the extents per disk volume. To debug file issues using this printed data, a user would need to manually review the data for each disk volume. This method can be tedious and time consuming.